This invention relates generally to rotary devices. More specifically, this invention relates to outer envelope trochoidal rotary devices.
Trochoidal rotary devices are constructed so that a rotor assembly planetarily rotates in a housing defining a cavity. Trochoidal rotary devices can be divided into two groups: inner envelope trochoidal devices; and outer envelope trochoidal devices. In an inner envelope trochoidal device, the rotor assembly includes apex seals that cooperate with the inner wall surface of the housing to define a plurality of discrete chambers. In an outer envelope trochoidal device the apex seals are mounted in the inner wall of the housing between individual working chambers. The peripheral surface of the rotor assembly cooperates with the apex seals to define a plurality of discrete chambers. Accordingly, the rotary assembly of an outer envelope trochoidal device functions, in part, to seal off the working chambers of the device. The peripheral surface of the rotor assembly and inner wall of the housing function as working chambers for expansion engines, compressors, expanders, meters, etc.
In an outer envelope trochoidal device, because the peripheral surface of the rotor assembly cooperates with the apex seals of the housing to provide a working chamber, it is necessary for the peripheral surface of the rotor assembly to have a construction that will create a seal between the rotor assembly surface and the apex seal. If a seal is not created between the apex seal and peripheral surface of the rotor assembly the efficiency of the engine or compressor will suffer. Indeed, U.S. Pat. No. 3,377,846 states that:
For greater simplification, the balancing of individual assemblies can be effected by using a standard mass and by equalizing the weights of all rotors in the course of manufacture. This requires that the rotors have a mass that can be reduced as necessary, which is often impossible because it is imperative not to drill holes in the peripheral surface or the sides in order not to break the continuity of these surfaces (against which the sealing elements rub). And even if the shape of the rotor should permit the provisions of easily accessible masses without the need to modify said surface in any way, the machining operation necessary on such masses is nonetheless very costly. (Column 1, lines 40-48).
As indicated above, in order to ensure that the rotor assembly planetates correctly in the rotor housing, the rotor assembly must be balanced. Typically, rotor assemblies are balanced by counterweights that are located on the shaft that planetates the rotor assembly. Although it is possible to balance the rotor assembly with these counterweights, it is usually difficult to make the fine balancing adjustments that may be needed. Moreover, due to the positioning of the counterweights on the shaft, it is difficult to access the counterweights if balancing adjustments must be made. Furthermore, as is also indicated by the quote from U.S. Pat. No. 3,377,846, in outer envelope trochoidal device the balancing of the rotor is hindered by the belief that the continuity of the peripheral surface must not be disturbed.
Accordingly, there is a need for an improved means for balancing rotor assemblies in outer envelope trochoidal devices.